This is what I did with my Funhouse...

Heat up the glue holding the insert with a hair dryer. You probably want the really hot setting and do this from under the playfield, not from the top. For the next bit, I used an old ball shooter with a rubber tip attached. Quickly and lightly, get a hammer and tap the insert into the playfield using the rubber tipped end of the ball shooter until it's level. Allow the glue to dry and that's it. If that doesn't do the trick you probably need to remove the insert (by heating the glue), clean off all the old glue from the insert and playfield and re-glue it.